Mini Chemistry
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G2 Science (Chemistry)

Build the Chemistry component shared by K223 and K225 through its syllabus-ordered topics, practice and review.

  • SEC G2 Science Chemistry component 2027
  • K223 / K225 · Singapore-Cambridge SEC
Learning goals
  • name appropriate apparatus for the measurement of time, temperature, mass and volume; including burettes, pipettes, measuring cylinders and gas syringes
  • suggest suitable apparatus, given relevant information, for a variety of simple experiments, including collection of gases.
  • describe methods of separation and purification for the components of mixtures, to include: — use of a suitable solvent, filtration and crystallisation or evaporation
  • describe methods of separation and purification for the components of mixtures, to include: — distillation and fractional distillation (see also 8.1(b))
  • describe methods of separation and purification for the components of mixtures, to include: — paper chromatography
  • suggest suitable separation and purification methods, given information about the substances involved in the following types of mixtures: — solid-solid
  • suggest suitable separation and purification methods, given information about the substances involved in the following types of mixtures: — solid-liquid
  • suggest suitable separation and purification methods, given information about the substances involved in the following types of mixtures: — liquid-liquid (miscible)
  • interpret paper chromatograms including comparison with ‘known’ samples (the use of Rf values is not required)
  • deduce from given melting point and boiling point data the identities of substances and their purity.
  • select and use techniques, apparatus and materials
  • take readings and record observations
  • interpret and evaluate experimental data and observations
  • evaluate methods and suggest possible improvements.
  • describe the solid, liquid and gaseous states of matter and explain their interconversion in terms of the kinetic particle theory and of the energy changes involved.
  • state the relative charges and approximate relative masses of a proton, a neutron and an electron
  • describe, with the aid of diagrams, the structure of an atom as consisting of protons and neutrons (nucleons) in the nucleus and electrons arranged in shells (energy levels) (knowledge of s, p, d and f classification is not required; a copy of the Periodic Table will be available in the examination)
  • define proton (atomic) number and nucleon (mass) number
  • interpret and use nuclide notations such as ¹²₆C
  • define the term isotopes
  • deduce the numbers of protons, neutrons and electrons in atoms and ions given proton and nucleon numbers.
  • describe the formation of ions by electron loss/gain and that these ions usually have the electronic configuration of a noble gas
  • describe, including the use of ‘dot-and-cross’ diagrams, the formation of ionic bonds between metals and non-metals, e.g. NaCl; MgCl2
  • relate the physical properties (including electrical property) of ionic compounds to their lattice structure.
  • describe the formation of a covalent bond by the sharing of a pair of electrons and that the atoms in the molecules usually have the electronic configuration of a noble gas
  • describe, using ‘dot-and-cross’ diagrams, the formation of covalent bonds between non-metallic elements, e.g. H2; O2; H2O; CH4; CO2
  • deduce the arrangement of electrons in other covalent molecules
  • relate the physical properties (including electrical property) of covalent substances to their structure and bonding.
  • describe the differences between elements, compounds and mixtures
  • describe the general physical properties of metals as solids having high melting and boiling points, malleable and good conductors of heat and electricity
  • describe an alloy as a mixture of a metal with another element, e.g. brass; stainless steel
  • identify representations of metals and alloys from diagrams of structures.
  • state the symbols of the elements and formulae of the compounds mentioned in the syllabus
  • deduce the formulae of simple compounds from the relative numbers of atoms present and vice versa
  • deduce the formulae of ionic compounds from the charges on the ions present and vice versa
  • interpret chemical equations with state symbols
  • construct chemical equations, with state symbols, including ionic equations.
  • define relative atomic mass, Ar
  • define relative molecular mass, Mr, and calculate relative molecular mass (and relative formula mass) as the sum of relative atomic masses
  • perform calculations involving the relationship between the amount of substances in moles, mass and molar mass (calculations of stoichiometric reacting masses and volumes of gases are not required).
  • describe the meanings of the terms acid and alkali in terms of the ions they produce in aqueous solution and their effects on Universal Indicator
  • describe neutrality and relative acidity and alkalinity, in terms of — relative H+ and OH– ion concentrations,
  • describe neutrality and relative acidity and alkalinity, in terms of — colour in Universal Indicator, and
  • describe neutrality and relative acidity and alkalinity, in terms of — the pH scale (calculation of pH from hydrogen ion concentration is not required)
  • describe the characteristic properties of acids as in reactions with metals, bases and carbonates to form salts (description of the preparation of pure salts is not required)
  • describe the reaction between hydrogen ions and hydroxide ions to produce water, H+ + OH– → H2O, as neutralisation
  • describe the importance of controlling the pH in soils and how excess acidity can be treated using calcium hydroxide
  • describe the characteristic properties of bases in reactions with acids and with ammonium salts
  • classify oxides as acidic, basic, amphoteric or neutral based on metallic/non-metallic character.
  • describe tests to identify the following gases: carbon dioxide (using limewater); hydrogen (using a burning splint); oxygen (using a glowing splint).
  • describe the Periodic Table as an arrangement of the elements in the order of increasing proton (atomic) number
  • describe how the position of an element in the Periodic Table is related to proton number and electronic configuration
  • explain the similarities between the elements in the same group of the Periodic Table in terms of their electronic configuration
  • describe the change from metallic to non-metallic character from left to right across a period of the Periodic Table
  • describe the relationship between number of outer (valence) electrons and metallic/non-metallic character
  • predict the properties of elements in Group 1 and Group 17 using the Periodic Table.
  • describe lithium, sodium and potassium in Group 1 (the alkali metals) as a collection of relatively soft, low density metals showing a trend in melting point and in their reaction with water
  • describe chlorine, bromine and iodine in Group 17 (the halogens) as a collection of diatomic non- metals showing a trend in colour, state and their displacement reactions with solutions of other halide ions
  • describe the lack of reactivity of the elements in Group 18 (the noble gases) in terms of their electronic configurations.
  • place in order of reactivity calcium, copper, (hydrogen), iron, lead, magnesium, potassium, silver, sodium and zinc by reference to the reactions, if any, of the metals with water, steam and dilute hydrochloric acid
  • deduce the order of reactivity from a given set of experimental results
  • describe the ease of obtaining metals from their ores by relating the elements to their positions in the reactivity series
  • describe the essential conditions for the corrosion (rusting) of iron as the presence of oxygen and water; prevention of rusting can be achieved by placing a barrier around the metal, e.g. painting; greasing; plastic coating.
  • name natural gas, mainly methane, and crude oil as non-renewable sources of energy
  • describe crude oil as a mixture of hydrocarbons and its separation by fractional distillation to yield fractions which have competing uses as fuels and as a source of chemicals (see also 1.2(a))
  • describe biofuel (exemplified by bioethanol from sugarcane) as a renewable alternative to natural gas and crude oil
  • describe how biofuel, when compared to fossil fuels, is more environmentally sustainable in terms of the offset in carbon dioxide emission during burning by that taken in during plant growth (see also 9(e)).
  • describe a homologous series as a group of compounds with a general formula, similar chemical properties and showing a gradation in physical properties as a result of increase in the size and mass of the molecules, e.g. melting and boiling points; viscosity
  • describe the alkanes as a homologous series of saturated hydrocarbons with the general formula CnH2n+2
  • draw the structures of unbranched alkanes, C1 to C3, and name the unbranched alkanes methane to propane
  • describe alkanes (exemplified by methane) as being generally unreactive except in terms of combustion and substitution by chlorine
  • describe the alkenes as a homologous series of unsaturated hydrocarbons with the general formula CnH2n
  • draw the structures of unbranched alkenes, C2 and C3, and name the unbranched alkenes ethene and propene
  • describe the manufacture of alkenes and hydrogen by cracking hydrocarbons and recognise that cracking is essential to match the demand for fractions containing smaller molecules from the refinery process
  • describe the difference between saturated and unsaturated hydrocarbons from their molecular structures and by using aqueous bromine
  • describe the reactions of alkenes (exemplified by ethene) in terms of combustion, polymerisation (see also 8.3(b)) and the addition with bromine and hydrogen
  • state the meaning of polyunsaturated when applied to food products
  • describe the manufacture of margarine by the addition of hydrogen to unsaturated vegetable oils to form a solid product.
  • describe polymers as large molecules built up from small units (monomers), different polymers having different units
  • describe the formation of poly(ethene) as an example of addition polymerisation of ethene as the monomer (see also 8.2(i))
  • state some uses of poly(ethene) as a typical plastic, e.g. plastic bags; clingfilm
  • deduce the structure of the addition polymer product from a given monomer and vice versa
  • describe the pollution problems caused by the disposal of non-biodegradable plastics
  • describe two methods of recycling plastics as — physical method (exemplified by melting small pieces of poly(ethene) waste into pellets)
  • describe two methods of recycling plastics as — chemical method (exemplified by cracking of plastic waste into fuel)
  • discuss the social, economic and environmental issues of recycling plastics.
  • describe the volume composition of gases present in dry air as being approximately 78% nitrogen, 21% oxygen and the remainder being noble gases (with argon as the main constituent) and carbon dioxide
  • name some common atmospheric pollutants, e.g. carbon monoxide; methane; nitrogen oxides (NO and NO2); ozone; sulfur dioxide; unburned hydrocarbons
  • state the sources of these pollutants as — carbon monoxide from incomplete combustion of carbon-containing substances
  • state the sources of these pollutants as — nitrogen oxides from lightning activity and internal combustion engines
  • state the sources of these pollutants as — sulfur dioxide from volcanoes and combustion of fossil fuels
  • discuss some of the effects of these pollutants on health and on the environment — the toxic nature of carbon monoxide
  • discuss some of the effects of these pollutants on health and on the environment — the role of nitrogen dioxide and sulfur dioxide in the formation of ‘acid rain’ and its effects on respiration and buildings
  • describe the carbon cycle in simple terms, to include — the processes of combustion, respiration and photosynthesis
  • describe the carbon cycle in simple terms, to include — how the carbon cycle regulates the amount of carbon dioxide in the atmosphere (see also 8.1(d))
  • state that carbon dioxide and methane are greenhouse gases and may contribute to global warming; give the sources of these gases and describe the potential effects of increased levels of these greenhouse gases, including more extreme weather events and melting of polar ice.

Start learning

Learn in order

Begin with Experimental Chemistry and follow the numbered roadmap.

Other ways to start

Foundations and evidence

  1. Experimental Chemistry

    Measure accurately, collect gases, separate mixtures and use physical evidence to judge purity.

  2. Particulate matter

    Build particle-state reasoning, then atomic and isotope structure, then ion and electron counting. Diffusion is not required.

  3. Bonding and structure

    Ionic and covalent bonding, structure–property links, metals and alloys. Metallic bonding and giant covalent structures are not required.

Calculations and reactions

  1. Chemical calculations

    Write formulae and equations, calculate relative masses, and convert directly between mass, moles and molar mass.

  2. Acid-base chemistry

    Ions, pH, reactions, neutralisation, soil treatment, bases and oxide classification.

  3. Qualitative analysis

    The three prescribed gas tests: carbon dioxide, hydrogen and oxygen.

Patterns and applications

  1. Periodic patterns

    Periodic trends, Groups 1, 17 and 18, the reactivity series, extraction and rust prevention.

  2. Organic chemistry

    Fuels, unbranched C1–C3 hydrocarbons, core alkane/alkene reactions and addition polymers.

  3. Air quality

    Air composition, pollutant sources and effects, the carbon cycle and greenhouse gases.

Practice and continue learning

  • Quiz practice — Choose G2 topic practice or a mixed course check.
  • Topic review — Choose a roadmap topic and work at the stated G2 boundary.
  • Revision guide — Review the G2 course map and choose your next step.

About this course

K223 / K225 Chemistry component · 2027

Study the SEC G2 Chemistry component shared by Science K223 and K225 in syllabus order, with practice and focused review routes.

The same Chemistry component is used by K223 Science (Physics, Chemistry) and K225 Science (Chemistry, Biology).

The roadmap descriptions state the G2 stopping point where a shared concept page also contains deeper G3 material.

Reviewed Jul 27, 2026

Questions about this course

Where should I start G2 Science Chemistry?

Start with the first roadmap topic on a first pass. During revision, return to the earliest topic you cannot complete independently.

What should I do when a topic is weak?

Use the topic guide to strengthen the explanation or calculation, then attempt a fresh question without notes before continuing.

When should I use mixed practice?

Use mixed practice to find weak areas. Then use topic practice and written responses to improve the exact reasoning that caused difficulty.

Review

Come back later to see whether your learning has lasted.

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